Dynamic Digital Displays (3D) Inc. was established to develop and market a high-performance Physician's Workstation with improved facilities for real-time, interactive three-dimensional (3D) visualization of human anatomy as derived from CT, MR or PET scans. A prototype device is already operational and generates shaded graphics images of 3D anatomy on a 2D video monitor at 15-20 frames/second. We anticipate this system will provide better tumor and normal tissue localization and identification for Radiation Therapy Planning (RTP), and are seeking SBIR funding to develop additional capabilities for this application area. Novel aspects will include interactive beam placement in 3D, simultaneous viewing of anatomy and dose distributions (using color for effective presentation), real-time rotation, and slice-planes to remove unwanted structures and obtain internal views. Phase I will comprise the specification, design and simulation of special features required for RTP; these will be integrated into the workstation during Phase II. Specific Phase I objectives are: (1) establish interactive features needed for RTP and determine their overall feasibility; (2) simulate these features with existing high-performance hardware and software; (3) evaluate results with clinical anatomy and dosimetry data; and (4) prepare detailed plans for the commercial prototype, to be implemented in Phase II.